Building Resilient APIs with .NET Core

01 Introduction

Building reliable web APIs requires more than just mapping database entities to JSON endpoints. In real-world enterprise software, APIs face unexpected failure modes: transient network timeouts, database lock contention, invalid payload schemas, and upstream microservice outages.

In this post, we will explore practical patterns in ASP.NET Core for building APIs that fail gracefully and recover predictably.

02 Validation & Standardized Error Contracts

One of the primary sources of API brittleness is inconsistent error responses. Clients should never parse HTML error pages or unhandled stack traces. Standardizing on RFC 7807 Problem Details provides predictable error payloads.

builder.Services.AddProblemDetails();
builder.Services.AddExceptionHandler<GlobalExceptionHandler>();

builder.Services.AddScoped<IOrderService, OrderService>();

By registering custom exception handlers, unhandled domain exceptions are safely mapped to HTTP status codes such as 400 Bad Request or 422 Unprocessable Entity without leaking server internals.

03 Resiliency & Retry Strategies

Distributed systems inevitably experience transient faults. Integrating Polly with HttpClientFactory allows us to configure exponential backoff retries and circuit breakers declaratively.

04 Comparing Architecture Approaches

When selecting architectural trade-offs, evaluate system complexity versus operational overhead: